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Have you ever get complaints from users stating “Network is too slow” ? how do you measure network throughput in your environment ? It is always good idea to benchmark your network(wired or wireless) performance. In this way when a user complaint about slowness, you can run a quick test again & compare it with your baseline performance results.

Iperf is great network performance testing tool (free ūüôā )you can use to measure throughput of a given network. In this post we will see how we can use it to measure wireless network performance. We will primarily focus on wireless performance testing & will use shown topology diagram where few different type of clients connect to my converged access setup.

wlan-iperf-11I have used a wired connected window PC as my iPerf server. You can simply download jperf from here. Once you download jperf-2.0.2 you can copy that onto your computer C: drive as shown below.

wlan-iperf-02Once you do this you can go to “C:\jperf-2.0.2\bin” in the command prompt as shown below. If you like to run this jperf app in graphical user interface (GUI) then you can run jperf.bat & you can follow this useful guide in that case.

wlan-iperf-03If you want to use it as “Iperf Server” you have to use “iperf -s” syntax. If you want to set it as “Iperf client” then you have to use “iperf -c <server-ip-address>” There are optional parameters you can set. You can view all of these “iperf -h” as shown below.

wlan-iperf-04Prior to measure wireless performance you need to make sure your wired network won’t be a bottleneck. Sometime there may be QoS policies throttling standard UDP/TCP port numbers used in this application. So it is good idea to benchmark using wired connection first & them move to wireless performance.

In my case I have connected my laptop onto 3850-1 via 1G Ethernet & run it as Iperf client. I have used 1s interval , 1MB as TCP window size & run it for 2min (120s),sometime if you leave default TCP window size, your throughput will reduced. So test it & use a value that gives close to expected results.

When you read this test result shown in below, it tells you about bandwidth available from iperf client to iperf server (ie client upload & server download). As you can see I got ~900Mbps.

C:\jperf-2.0.2\bin>iperf -c x.x.13.31 -i 1 -t 120 -w 1M
------------------------------------------------------------
Client connecting to x.x.13.31, TCP port 5001
TCP window size: 1.00 MByte
------------------------------------------------------------
[168] local x.x.13.20 port 56898 connected with x.x.13.31 port 5001
[ ID] Interval       Transfer     Bandwidth
[168]  0.0- 1.0 sec   105 MBytes   885 Mbits/sec
[168]  1.0- 2.0 sec   105 MBytes   881 Mbits/sec
[168]  2.0- 3.0 sec   112 MBytes   939 Mbits/sec
[168]  3.0- 4.0 sec   107 MBytes   897 Mbits/sec
[168]  4.0- 5.0 sec   106 MBytes   888 Mbits/sec
[168]  5.0- 6.0 sec   109 MBytes   914 Mbits/sec
.
.
[168] 110.0-111.0 sec   108 MBytes   906 Mbits/sec
[168] 111.0-112.0 sec   111 MBytes   933 Mbits/sec
[168] 112.0-113.0 sec   109 MBytes   916 Mbits/sec
[168] 113.0-114.0 sec   111 MBytes   927 Mbits/sec
[168] 114.0-115.0 sec   108 MBytes   908 Mbits/sec
[168] 115.0-116.0 sec   111 MBytes   934 Mbits/sec
[168] 116.0-117.0 sec   111 MBytes   930 Mbits/sec
[168] 117.0-118.0 sec   111 MBytes   930 Mbits/sec
[168] 118.0-119.0 sec   111 MBytes   933 Mbits/sec
[168] 119.0-120.0 sec  76.4 MBytes   641 Mbits/sec
[168]  0.0-120.0 sec  12.6 GBytes   903 Mbits/sec

To measure the client download, you can run “iperf -s” on the PC you ran as client previously. I have used 1M as TCP window size. This time¬† you have to run “iperf -c x.x.13.20” command on the other PC.

C:\jperf-2.0.2\bin>iperf -s -w 1M
------------------------------------------------------------
Server listening on TCP port 5001
TCP window size: 1.00 MByte
------------------------------------------------------------
[268] local x.x.13.20 port 5001 connected with x.x.13.31 port 58151
[ ID] Interval       Transfer     Bandwidth
[268]  0.0-120.0 sec  11.5 GBytes   823 Mbits/sec

You can export these data onto excel & graph it for nice representation.(you can simply hold Alt button in windows & copy only the data rate values ūüôā ). So here is my graph look like for wired bandwidth performance.

wlan-iperf-05Let’s see now how can we measure the wireless performance. In my case I have created a SSID (Open Auth simpliciy) on my 3850 MA & 3700 AP register to it. So this is the simplest without any QoS policies on it.

wlan ABC 20 ABC
 no broadcast-ssid
 client vlan 1410
 no security wpa
 no security wpa akm dot1x
 no security wpa wpa2
 no security wpa wpa2 ciphers aes
 no shutdown

My AP is running on power level 5 & DCA channel width set to 80MHz. You can verify it shown as below

3850-2#show ap dot11 5ghz summary 
AP Name            MAC Address     Slot  Admin State  Oper State  Channel             Width  TxPwr   
---------------------------------------------------------------------------------------------------
3702-1             b838.6184.c670     1  Enabled      Up          (161,157,149,153)*     80    5(*)  

Here I have connected a MacBookAir,Nexus 5 phone, Dell E6430, Dell E7440 to my AP for testing. You can get the details of client RSSI/SNR from the switch itself. I had trouble with AC-7260 driver getting this detail & this NIC/driver is giving some grievance to many of us(Here is some detail & I am using  17.0.5.8 driver version in this NIC)

3850-2#show wireless client summary                                          
Number of Local Clients : 4
MAC Address    AP Name      WLAN State              Protocol 
---------------------------------------------------------------
6067.2077.5470 3702-1        20   UP                 11n(5) <-Dell E6430   
8086.f2cd.3c5f 3702-1        20   UP                 11ac <-Dell E7440     
bcf5.acfe.eb1c 3702-1        20   UP                 11ac <-Nexus 5
8438.3540.2100 3702-1        20   UP                 11ac  <-MBA 

**** MBA ****
3850-2#sho wireless client mac-address 8438.3540.2100 detail | in Signal|Rate
Current Rate : 12.0
Supported Rates : 12.0,24.0,36.0,48.0,54.0,12.0,24.0,36.0,48.0,54.0
  Radio Signal Strength Indicator : -40 dBm
  Signal to Noise Ratio : 52 dB

**** NEXUS 5 ****
3850-2#sho wireless client mac-address bcf5.acfe.eb1c detail | in Signal|Rate
Current Rate : m7
Supported Rates : 12.0,24.0,36.0,48.0,54.0,12.0,24.0,36.0,48.0,54.0
  Radio Signal Strength Indicator : -29 dBm
  Signal to Noise Ratio : 58 dB

*** DELL E6430 (N6205) ****
3850-2#sho wireless client mac-address 6067.2077.5470 detail | in Signal|Rate
Current Rate : m15
Supported Rates : 12.0,24.0,36.0,48.0,54.0,12.0,24.0,36.0,48.0,54.0
  Radio Signal Strength Indicator : -29 dBm
  Signal to Noise Ratio : 63 dB

*** DELL 7440(AC-7260) different to all others ****
3850-2#sho wireless client mac-address 8086.f2cd.3c5f detail | in Signal|Rate
Supported Rates : 12.0,24.0,36.0,48.0,54.0,12.0,24.0,36.0,48.0,54.0
  Radio Signal Strength Indicator : Unavailable
  Signal to Noise Ratio : Unavailable

Now on your wireless client (first in MacBookAir) if you run “iperf -c x.x.13.20 -i1 -t 120 -w 1M” you can measure the wireless client upload performance. As you can see below I got average 294 Mbps for wireless upload speed for this client.

Something:~ $ iperf -c x.x.13.20 -i1 -w 1M -t 120
------------------------------------------------------------
Client connecting to x.x.13.20, TCP port 5001
TCP window size: 1.00 MByte (WARNING: requested 1.00 MByte)
------------------------------------------------------------
[  4] local 10.141.96.19 port 54005 connected with x.x.13.20 port 5001
[ ID] Interval       Transfer     Bandwidth
[  4]  0.0- 1.0 sec  28.8 MBytes   241 Mbits/sec
[  4]  1.0- 2.0 sec  44.8 MBytes   375 Mbits/sec
[  4]  2.0- 3.0 sec  40.9 MBytes   343 Mbits/sec
[  4]  3.0- 4.0 sec  38.2 MBytes   321 Mbits/sec
[  4]  4.0- 5.0 sec  39.9 MBytes   334 Mbits/sec
[  4]  5.0- 6.0 sec  43.2 MBytes   363 Mbits/sec
.
.
[  4] 117.0-118.0 sec  42.9 MBytes   360 Mbits/sec
[  4] 118.0-119.0 sec  49.5 MBytes   415 Mbits/sec
[  4] 119.0-120.0 sec  42.6 MBytes   358 Mbits/sec
[  4]  0.0-120.0 sec  4.10 GBytes   294 Mbits/sec

If you run “iperf -s¬† -w 1M” on my MBA & run “iperf -c 10.141.96.19 -i 1 -t 120 -w 1M” command on wired PC I can measure the wireless client download performance. Here is the wireless download performance (avg 304 Mbps) for MBA

C:\jperf-2.0.2\bin>iperf -c 10.141.96.19 -i 1 -t 120 -w 1M
------------------------------------------------------------
Client connecting to 10.141.96.19, TCP port 5001
TCP window size: 1.00 MByte
------------------------------------------------------------
[168] local x.x.13.20 port 55232 connected with 10.141.96.19 port 5001
[ ID] Interval       Transfer     Bandwidth
[168]  0.0- 1.0 sec  53.3 MBytes   447 Mbits/sec
[168]  1.0- 2.0 sec  48.2 MBytes   404 Mbits/sec
[168]  2.0- 3.0 sec  48.3 MBytes   405 Mbits/sec
[168]  3.0- 4.0 sec  49.5 MBytes   415 Mbits/sec
[168]  4.0- 5.0 sec  51.6 MBytes   433 Mbits/sec
[168]  5.0- 6.0 sec  52.6 MBytes   442 Mbits/sec
[168]  6.0- 7.0 sec  53.5 MBytes   449 Mbits/sec
.
.
[168] 116.0-117.0 sec  43.3 MBytes   364 Mbits/sec
[168] 117.0-118.0 sec  40.9 MBytes   343 Mbits/sec
[168] 118.0-119.0 sec  43.8 MBytes   367 Mbits/sec
[168] 119.0-120.0 sec  11.2 MBytes  93.9 Mbits/sec
[168]  0.0-120.2 sec  4.26 GBytes   304 Mbits/sec

For any Android device you can install iperf application from Play Store for free ūüôā & then you can run these iperf client server commands. Here is a snapshot of Nexus 5 phone running as iperf client. For iOS device you have to pay ;(

wlan-iperf-07Like this I have run this performance testing for all those clients mentioned & export that data onto excel. So here is the result I got for 3 clients who supports 802.11ac. As expected, MBA gave me the best performance out of these 3 devices.As you can see below I got less than 100Mbps (less than 1/3 of equivalent MBA) download speed for Intel AC7260 (though it is two spacial stream client). Even Nexus 5 (single SS clinet) performed much better in downloads. You may surprised ūüėĮ by this result, but such is the way of life with this Intel 7260 driver.

wlan-iperf-08Just to compare, I have done the test with Intel N6205 (802.11n) & compare the result with Intel N7260(802.11ac 2 SS). As you can see below you will get marginal differences between those two.

wlan-iperf-09 Hope this is useful to you as well. When next time you get a slowness  complaint, always measure network performance like this.

PS: There are lots of commercial apps available if you willing to pay for these type of testing. I have given you a simpler method & cost you nothing, but you have to do some manual work.

 related posts

1. 802.11ac with Cisco 3700AP